, and bill weir in new york city. this is "nightline." september 7th, 2012. >>> good evening. i'm cynthia mcfadden. tonight, pregnant at 61. when her young daughter needed a surrogate, one woman stepped up, giving birth and becoming a grandmother at the same time. and she is not alone. in fact, an illinois woman gave birth to her granddaughter just last week. but to quote president lyndon johnson, our problem is not making miracles. it's managing them. just because a woman can do this, doesn't mean that she should. here's abc's amy robach with one family's story. >> reporter: little finn and his 61-year-old grandmother christine casey share a very rare bond. not only is she his grandmother, but she's also his surrogate mother. >> how could that possibly happen? no offense, but who would do that? and what doctor would let them do that? >> we kept thinking, we were going to be stopped anywhere along the way. at every turn, they kept saying, well, you're really in amazing shape. >> reporter: chris gave birth to her grand